diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 5597d222b..7c3521432 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Expanded home-relative marketplace catalog paths before cache access, preventing updates from writing into a literal `~` directory under the process working directory ([#8627](https://github.com/can1357/oh-my-pi/issues/8627)).
+
 ## [17.3.4] - 2026-08-14
 
 ### Changed
diff --git a/packages/coding-agent/src/extensibility/plugins/marketplace/manager.ts b/packages/coding-agent/src/extensibility/plugins/marketplace/manager.ts
index 79002fd8c..72733e9f3 100644
--- a/packages/coding-agent/src/extensibility/plugins/marketplace/manager.ts
+++ b/packages/coding-agent/src/extensibility/plugins/marketplace/manager.ts
@@ -11,6 +11,7 @@ import * as os from "node:os";
 import * as path from "node:path";
 
 import { isEnoent, logger, pathIsWithin } from "@oh-my-pi/pi-utils";
+import { expandTilde } from "../../../tools/path-utils";
 import { normalizePluginRuntimeConfig } from "../runtime-config";
 import type { PluginRuntimeConfig } from "../types";
 
@@ -107,12 +108,11 @@ export class MarketplaceManager {
 		}
 
 		const sourceType = classifySource(source);
-		const normalizedSource =
-			sourceType === "local"
-				? path.resolve(source.startsWith("~/") ? path.join(os.homedir(), source.slice(2)) : source)
-				: source;
+		const normalizedSource = sourceType === "local" ? path.resolve(expandTilde(source)) : source;
 
-		const catalogPath = path.join(this.#opts.marketplacesCacheDir, catalog.name, "marketplace.json");
+		const catalogPath = path.resolve(
+			expandTilde(path.join(this.#opts.marketplacesCacheDir, catalog.name, "marketplace.json")),
+		);
 
 		// Persist the fetched catalog so subsequent reads don't require re-fetching.
 		await Bun.write(catalogPath, `${JSON.stringify(catalog, null, 2)}\n`);
@@ -174,11 +174,13 @@ export class MarketplaceManager {
 			await promoteCloneToCache(clonePath, this.#opts.marketplacesCacheDir, catalog.name);
 		}
 
-		// Overwrite cached catalog
-		await Bun.write(existing.catalogPath, `${JSON.stringify(catalog, null, 2)}\n`);
+		// Overwrite the cached catalog and migrate legacy home-relative registry entries.
+		const catalogPath = path.resolve(expandTilde(existing.catalogPath));
+		await Bun.write(catalogPath, `${JSON.stringify(catalog, null, 2)}\n`);
 
 		const updatedEntry: MarketplaceRegistryEntry = {
 			...existing,
+			catalogPath,
 			updatedAt: new Date().toISOString(),
 		};
 
@@ -893,14 +895,13 @@ export class MarketplaceManager {
 	}
 
 	async #readCatalog(entry: MarketplaceRegistryEntry): Promise<MarketplaceCatalog> {
+		const catalogPath = path.resolve(expandTilde(entry.catalogPath));
 		try {
-			const content = await Bun.file(entry.catalogPath).text();
-			return parseMarketplaceCatalog(content, entry.catalogPath);
+			const content = await Bun.file(catalogPath).text();
+			return parseMarketplaceCatalog(content, catalogPath);
 		} catch (err) {
 			if (isEnoent(err)) {
-				throw new Error(
-					`Marketplace catalog not found at ${entry.catalogPath}. Try: /marketplace update ${entry.name}`,
-				);
+				throw new Error(`Marketplace catalog not found at ${catalogPath}. Try: /marketplace update ${entry.name}`);
 			}
 			throw err;
 		}
@@ -918,14 +919,10 @@ export class MarketplaceManager {
 	 */
 	#resolveMarketplaceRoot(entry: MarketplaceRegistryEntry): string {
 		if (entry.sourceType === "local") {
-			// expandHome already happened in fetcher; resolve to ensure absolute.
-			const expanded = entry.sourceUri.startsWith("~/")
-				? path.join(os.homedir(), entry.sourceUri.slice(2))
-				: entry.sourceUri;
-			return path.resolve(expanded);
+			return path.resolve(expandTilde(entry.sourceUri));
 		}
 		// For git/github/url sources, the catalog lives at <cloneDir>/marketplace.json
 		// under marketplacesCacheDir/<name>/; parent = <marketplacesCacheDir>/<name>/
-		return path.dirname(entry.catalogPath);
+		return path.dirname(path.resolve(expandTilde(entry.catalogPath)));
 	}
 }
diff --git a/packages/coding-agent/test/marketplace/manager.test.ts b/packages/coding-agent/test/marketplace/manager.test.ts
index 1097ee250..1f608832b 100644
--- a/packages/coding-agent/test/marketplace/manager.test.ts
+++ b/packages/coding-agent/test/marketplace/manager.test.ts
@@ -9,6 +9,8 @@ import { PluginManager } from "@oh-my-pi/pi-coding-agent/extensibility/plugins/m
 import {
 	MarketplaceManager,
 	readInstalledPluginsRegistry,
+	readMarketplacesRegistry,
+	writeMarketplacesRegistry,
 } from "@oh-my-pi/pi-coding-agent/extensibility/plugins/marketplace";
 import * as piUtils from "@oh-my-pi/pi-utils";
 import { removeSyncWithRetries } from "@oh-my-pi/pi-utils";
@@ -168,6 +170,34 @@ describe("MarketplaceManager", () => {
 		expect(new Date(updated.updatedAt) >= new Date(added.addedAt)).toBe(true);
 	});
 
+	it("updateMarketplace expands a home-relative catalog path", async () => {
+		const fakeHome = fs.mkdtempSync(path.join(ctx.tmpDir, "home-"));
+		const homedirSpy = spyOn(os, "homedir").mockReturnValue(fakeHome);
+		const registryPath = path.join(ctx.tmpDir, "marketplaces.json");
+		const originalCwd = process.cwd();
+		const cwd = path.join(ctx.tmpDir, "cwd");
+
+		try {
+			const added = await ctx.manager.addMarketplace(FIXTURE_DIR);
+			const catalogPath = "~/.omp/plugins/cache/marketplaces/test-marketplace/marketplace.json";
+			const registry = await readMarketplacesRegistry(registryPath);
+			await writeMarketplacesRegistry(registryPath, {
+				...registry,
+				marketplaces: [{ ...added, catalogPath }],
+			});
+			fs.mkdirSync(cwd);
+			process.chdir(cwd);
+
+			await ctx.manager.updateMarketplace("test-marketplace");
+
+			expect(fs.existsSync(path.join(fakeHome, catalogPath.slice(2)))).toBe(true);
+			expect(fs.existsSync(path.join(cwd, catalogPath))).toBe(false);
+		} finally {
+			process.chdir(originalCwd);
+			homedirSpy.mockRestore();
+		}
+	});
+
 	// ── Plugin discovery ───────────────────────────────────────────────────
 
 	it("listAvailablePlugins → returns catalog entries", async () => {